Make-busy scheme for telephone systems



my 12, 192s. 1,537,326 B. D. WlLLS MAKE BUSY SCHEME FOR TELEPHONESYSTEMS Filed Aug; 28, 1,922 h h r@ j j L er1-Land D -l1-M115 PatentedMay 1,2, 1925.

yUNITED STATES PATisu'r OFFICE.,

BERNARD MAKE-BUSY SCHEME FOR TELEPHONE SYSTEMS.

v'Appueauon` inea August 2s, 1922. serial No. 584,7e1. f

To all 'whom t may concern.'

Re it known that I, Buurman D. `vVinLrs,

a citizen ot the United States oi' America, and a resident of Oak Park,Cook County, and State of Illinois, have invented certain new and usefulImprovements in Make-Busy Schemes for Telephone Systems, otn which thefollowing is a specification.y 1 i The present inventiony relates tomake busy schemes for telephone systems in general, Vbut is moreparticularly applicable to make busy schemes for telephone systems inwhich primary and secondary trunking is used, and the principal objectis the production ot' a new and improved arrangement ior making busyalll the idle secondary switches of a group as soon as all the trunksaccessible thereto become busy.

So far -as applicant knows, it has been the practice in' primary andsecondary trunking systemsto use one chain relay persecondary trunk tormaking a secondary-group busy when all the secondary trunks become busy.lWhile this arrangement has proven fairly successful -from anoperating,standpoint, it

desirable from an economical Vstandpoint to reduce the equipment and tosimplify the arrangement.` llhis is done according to the presentinvention by providing one relay per group of trunks, which relay isnormally short circuited by a ground. potential which is placed on aconnnon conductor. by each of the switches to which the trunksaccessible to a secondary group extend. This ground potential is removedby the'switches y in succession as they become busy and, when the lastswitch becomes busy, the shunt 1s linally ren'ioved 'trom `the. commonrelay,`

whereupon the group is made busy.

A1ccording to another 'jeature ot the invention, the same principle isapplied to a secondary group in which partot the trunks are individualto the group and other trunks are common to this group and to as manyothers asV desired. In this case,fthe group make-busy relay iscontrolled from the individual trunks and a similar relay is controlledby the common trunks, and therelay of the common group 'maintains themake-busy relay shunted until the last common trunk becomes busy.

Another object is to arrange the selectors which are accessible to thesecondary switches so that theycontrol the sliunting ground with theaddition of amountr of equipment.V

Referring now to the drawings,V which comprise a single sheet, there isshown a line switch 'C individual to the line of suba minimum station A,and having access to the secondy switch 'D are of the well-known rotarytype, in winch the wipers have no normal position. and move m a forwarddirection only, while the selectors suoli as E are ot' the well-known D.WILLIS, OF OAK PARK, ILLINOIS, ASSIGNOR T0 AUTOMATIC ELECTRIC i COMPANY,OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS. i y

sal

vertical and rotary type, and, accordingly, f

have 100 sets of bank contacts which are arrangedV in ten horizontalrows or levels.

The circuits of the switches C and l) are well-known and likewisethecircuits of the selectors such as E, with the exception of theaddition ot the lower contact of oliir1 normal spring 73 andtheassociated conductor and the improved make-busy jack il.

Perhaps the apparatus shown vwill be understood better in vconnectionwith its operation when a call is being through.

Then thereceiver is removed at substation A, a circuit-is closedoverline conductors 11 and 12 for line relay 14 of the line switch-C.Relay 14, upon energizing, places ground upon private normal conducto-1'10 at armature 20, thereby making the calling line busy, and closingcircuit for switching relay 13 and stepping magnet 15 in series, and atarmature 19 connects test wiper 22 to the junction of switching relay 13and stepping magnet 15. AIn casethe trunk upon which the wipers arestanding is idle, the connecting up ofthe test wiper has noparticularifunctionV and switching relay 13 energizes immediately.Assuming the trunk to be busy, however, switching relay 13 is shortcircuited by the ground ypotential which is presenten the test contactthere.- of, and the wipers 21-23, inclusive, are advanced in search ofan idle. trunk by the buzextended there-k zer-like action `of steppingmagnet 15, which operates through test Wiper 22. llVhen an idle trunk isreached, which trunk it will be assumed is the one extending to thesecondary switch D, switching relay 13, being no longer shortcircuited,energizes in series w ith stepping magnet 15, 4stepping magnet`15 not energizing on account of the high resistance of switching relay13. Upon energizing, switching relay 13 opens the test circuit andprepares ,the holding circuit at armature 17, and at armatures 16 and 16disconnects line conductors 11 .and 12 from the Winding of line relay 14and ground, and extends them by way of wipers 21 and 23, conductors 24.-and 26, and armatures 30 and 33 to the winding ol*l line relay 28 of thesecondary switch D and ground, respectively. Line relay Q8,uponenergizing, places ground on release trunk conductor 25 at armature36, thereby establishing the usual holding circuitfor switching relay 13of the line switch C before slow acting relay 14 has had time todcenergize. :is a further result of the energization koli' relay 28, itcloses a circuit for switching relay 2,7 and stepping magnet 29 inseries at armature 35, and at armature 34 connects test wiper 38 to thejunction of the switching relay and the stepping magnet. The secondaryswitch i) new operates in the `same manner as the line switch C toselect an idle trunk, which trunk it will be assumed is the onecomprising conductors lO-flQ, inclusive, and extending to the selectorE. Switching relay 27, upon energizing, when the idle trunk is reached,extends release trunk conductor 25 through to test Wiper 33 at armature32; opens the test circuit and prepares the holding circuit for relay 27at armature 31; and at armatures 30 and 33 disconnects conductors 24eand 26 from the Winding .of line relay 23 and ground, and entends themVby way yof wipers 37' and 39, conductors 40 and 42, and armatures 8,2and 85 and their resting contacts to the windings of line relay 65 ofselector E. Line relay A65, upon energizing, removes ground at one pointfrom the common lconductor 55, and closes a circuit tor release relay 664at armature 76, which .circuit includes armature S-l and its restingcontact and the normal contact ot the jack J. Release relay 66, uponenergizing, discon- -nects the resting contactof armature 76 from acircuit tor vertical magnet 7 0 by Way ol' armature 78 and its workingcontactand series relay 67. By the operation oit vertical magnet 70, theswitch Wipers 86-88, inclusive, are raised opposite the desired level ofbank contacts. Slow acting series relay 67 is maintained energized inseries with vertical magnet 70 throughout the vertiral movement and, inconjunction with the oil normal contacts 7l, which close upon the lirstvertical step, closes a circuit for stepping relay 68 by way ot'inter-rupeter contacts 7 5. Stepping relay 68, upon energizing, closes alocking circuit tor itself at armature 8O and at armature 81 prepa-res acircuit for rotary magnet 71.

At the .end ol the Vertical n'iovement, slow acting relay 67 deenergizesand closes the circuit of rotary magnet 71 at armature 79. Rotary magnet71, upon energizing, advances the wipers 86-88, inclusive, intoengagement with the .first set ot bank contacts in the level oppositewhich they are raised and, near the end ot its stroke, opens the circuitet stepping relay 63. Stepping relay 68, upon deenergizing, opens thecircuit oi rotary magnet 71 at armature S1, whereupon rotary magnet Y71deenergizes and closes its interrupter contacts 75 again. ln case thetrunk terminating in the' first set of bank contacts is idle, switchingrelay 69 energizes in series with stepping relay 68 at this time.lffrssuming the trunk to be busy, however, switching relay 69 is shortcir-- cuited and relay o8, upon energizing, closes a circuit jtor rotarymagnet 71, whereupon the s'fitch wipers are advanced into engagementwith the next set of kbank contacts. This operation continues until anidle trunk is reached, which trunk it will be assumed is the oneterminating' in bank contacts 39-91, inclusive, whereupon switching relay 69, being' no longer short circuited, energizes over the Jfollowingcircuit: From ground bywvay o'f the working); contact of armature 77 andsaid armature, switching relay 69, off normal contacts 7l, interruptercontacts 75, and stepping relay 63 to battery. Stepping relay 68 doesnot energize at this time, however, owing to the high resistance ofswitching relay 69, Switching relay 69, upon energizing, disconnectsground 'from armature 76 ot' line relay 65 at armature Si, therebyopening the circuit of release relay 66; opens the test circuit andprepares the holding circuit at armature 83; and at armatures 32 aud 35disconnects conductors Ll() and 4t2 troni relay 653 and extends them byway ,ot wipers 86 and 83 and bank contacts 89 and 91 to the windings othe line relay of the switch to which the seized trunk extends. Thenthis occurs, the line and release relays (not shown) of the seized trunkenergize, whereupon the latter places ground upon the associated lsition in the usual manner. Then the shaft of the selector E reachesnormal position,

release trunk conductor, ythereby establishing the usual holdingkcircuit for the switches C, D, and E before the release relay 66'hashad timeto deenergize. s

The calling subscriber may now entend the connection on to the desiredline ,in the usual manner and, whenV he replaces his receiver at the endof the conversation, ground is removed from the release trunk conductorof the trunk seized bythe selector VE, whereupon the switching relays1.2i, 27, Yand 69 of the switches C, D, and E, respectively,deenergize.Y Switching relay 69, upon def energizing, closes a circuitfor release magnet 72 as follows: from ground by way of the normalcontact ofthe jack J, resting contact of armaturefSa and said armature,armature A76 and its resting contact, armature 78 and its restingcontact, off normal spring 7 3 and its upper contact, and release magnet72 to battery. Upon the energization of release magnet 72, the shaft andwipers of the selector E are restored to normal ponet 72k and appliesgroundto conductor 55.

vThe operation of the make-busy equipment will now be taken up a littlemore in detail. It was pointed out above that the` Y selector E removesground vfrom conductor upon being seized, and replaces the ground whenit becomes idle and is restored to normal.` Assuming now thatthe groundpotential. is removed from conduc tor 55 by all of the selectors, suchas E, individual to the group; conductor 55 remains groundedbyarmature53 of relay 50 which` is associated with the trunks which arevcommon to several secondary groups.

Assuming further that thel common trunks also become busy, groundisremoved fromV sistance 57 and makes all the idle secondary lineswitches in the group busy, the trunk extending to the switch D forexample, being made busy through the resting 'contact of armature 32andsaid armature.V

As soon as a trunk becomes available in either the common group or theindividual group, the secondary group in question rendered idle again.For example, if one of the selectors such as E places ground onconductor 55, upon being restored to normal, relay 54 is short circuitedand deenergizes, or if one of the selectors such as E places ground onconductor L51 of the common group of trunks, relay 50 is short circuitedgizes also.

ground on and upon deenergizing, places 54 deeper'- conductor 55,whereupon relay` In case it is desired to make a particular Yswitchwhich is accessible to a secondary switch busy, 1t is necessary to dotwo things.

ground from conductor 55 by `the lower spring of the jack J moving outof engagement with its normal contact.

V What is claimed is:

1. n a trunking system, a group of trunks, a l switch having accessthereto, a conductor common to said group maintained at a certainpotential at each of said trunks, means for taking said trunks for use,means responsive to the takingvfor use of each of said trunks forremoving said certain potential from said conductor at one point, andmeans responsive to the removal of said cer` tain potential at'the lasttrunk to bevtaken for use for rendering said switch non-selectable. n 2.In a trunking system a lirst group of switches, a lirst group or' trunksaccessible thereto, a 'second grouproi" switches, a second group oftrunks accessible to both said groups or' switches in common, a lirstand a second conductor common to said first and said second groups oftrunks, respectively each of said conductors being maintained at acertain potential byeach ofthe trunksin the grou-p to which it iscommon, means confA trolled oversaid second conductorfor main-v tainingsaid lirst conductor at said certain potential at still another point,kmeans for taking saidv trunks for use, means respon# sive to the takingfor use of each of said trunks for removing said certain potential fromthe associated common conductor at one point, means'responsive to theremoval of said potential from said second conductor at all points forremoving said potential from said first conductor at said other point,and means responsive to the removal of said certain potential from saidfirst conductor at all points for rendering'said first group oi"switches non-selectable. v s

3. In a telephone system, a firstgroup of switches, a second group ofswitches accessible to said first group,feach of the switches in saidsecond group having line, holding, and release relays, and normallyclosed olf normal contacts, normally closed contacts on each ofsaidrelays, a conductor common to 4 Las maintained at a ground potential byeach of said switches through said normally closed contacts on each otthe relays named and said ofi normal contacts in series, means fortaking each of said switches for use, means effective while one of saidswitches is in use for removing the ground potential from said commonyconductor at that point by main taining ,open one or more of saidnormally closed contacts, and means .controlled by the remoyalfot saidground potential from said conductor at all points for rendering saidfirst group ot switches non-selectable.

4i. In a trunking systeim a group of trunks, a switch having' accessthereto, a conductor common to said group being tained at a certainpotential at each of said trunks, means for taking said trunks for use,means responsive to the takingY for use of each of said trunks torremoving said certain potential from said conductor at one point, meansresponsive to the removal of said certain potential at the last trunk tobe taken for use tor rendering said switch non-selectable, a jack foreach of said trunks, and means responsive to plugging into one otsaidjacks for rendering the associated trunk nonselectable and tor removingsaid certain potential from said conduct-or at ,that point, i

5. The combination, with group or' automatic switches, of a guardingcircuit includinera relay and a source ot current, a pa.- 4of contactsat each switcn for shortcircniting said relay, and means in each switch:tor opening the associated contacts when the switch is operated.

6. The combination, with two groups of automatic switches, oia aguarding, circuit for ,the lirst group of switches controlled jointly bythe switches in the second group, said circuit including` a relay and asource of current, contacts on a switch in the second lgroup vformaintaining said relay short circuited while the switch is in normalposition, and similar contacts on each ot the other switches in thesecond group. Y

7. 'The combina'tiOn, 4with a group of switches, of a relay, and meansfor operating said relay only when all said switches are in use, saidi'ueans comprising a closed cnciut tor said relay, and means in eachswitch ell'ective while the switch idle tor maintaining said relay shortcircuited.

8. ln a telephone system, a group ot' lines, an electro-magnet common tosaid lines. a circuit tor said magnet including a source ot' current, apair of contacts individual to each line` circuits over which all saidpairs oi contacts are connected in parallel with each other and in shuntof said rela-y, and means for `opening each pair of lcontacts when theassociated line is in use. y

9. ln a telephone system, a group Voit lines, an electro-magnet commonto `said lines, a circuit Jfor said magnet including a source ofcurrent, a pair ci contacts individual to each line, circuits over whichall `said pairs of contacts are connected in parallel with each otherand in shunt .ot said reay, means for opening each ,pair of ,contat-tswhen the associated line is in use, and a. resistance included in saidcircuit to prevent excessive current How while said magnet isshort-circuited.

in a telephone system,A an automa-tic switch, a guarding circuit commonto said switch and other similar switches, a line relay in said switchhaving a pair of contacts, an operating ,circuit Vfor the switch overwhich said contacts transmit impulses when the switch is in use, and abranch of said guarding .circuit on which said contactg maintain apotential while the switch is idle.

ll. In a telephone system, an automatic switch, a guarding circuithaving a branch incoming to said switch, a Vrelease magnet for saidswitch, a locali switch conductor connected to a source of current,means for connecting said conductor to said magnet to release saidswitchand vmeans responsive to the restoration of said switch fordisconnecting said conductor from said magnet and tor connecting it tothe said branch of said guarding circuit.

In witness whereof, I hereunto subscribe myl name this 25th day ofAugust, A. D.. 1922.

BERNARD D. WILLIS.

DISCLAIMER.

1,537,326.-Bcmm"el D. Willis` Oak Park, Ill. MAKE-BUSY SCHEME ronTELEPHONE SYSTEMS. Patent dated May 12, 1925. Disclaimer filed May 20,1926, by the assignee, Automatic E lcctrz'c Inc.

Hereloy enters a disclaimer Ito. claims 1, 5, 7, 8, and 9 in saidspecification, which are in the following words, to wit:

l. In a trunking system, a group of trunks, a switch having accessthereto, a conductor common to said group maintained at a certainpotential at each of said trunks, means for taking said trunks for use,means responsive to the taking for use of each of said trunks forremoving said certain potential from said conductor at one point, andmeans responsive to the removal of said certain potential at the lasttrunk to b e taken for use for rendering said switch non-selectable.

5. The combination, with a group of automatic switches, of a guardingcircuit 'including a relay and a source ot current, a pair of contactsat eac-l1 switch for shortcircuiting said relay, and means in eachswitch for opening the associated contacts when the switch is operated.

7. The combination, with a group of switches, of a. relay, and meansforoperating said relay only when all said switches are in use, said meanscomprising a closed circuit for said relay, and means in each switcheffective while the switch is idle for maintaining said relay shortcircuited.

18. In a telephone system, a group of lines, an electro-magnet common tosaid lines, a circuit for said magnet including a source of current, apair of contacts individual to each line, circuits over which all saidpairs of contacts are connected in parallel with each other and in shuntot said relay, and means for opening each air of contacts when theassociated line is in use.

9. In a telephone system, a group of lines, an electro-,magnet common tosaid lines, a circuit :tor said magnet including a source of current, apair of contacts individual to each line, circuits over which all saidpairs of contacts are connected in parallel with each other and in shuntof said relay, means for opening each pair of contacts when theassociated line is in use, and a resistance included in said circuit toprevent excessive current flow while said magnet is short-circuited.

[,Ojicz'al Gazette June 8, 1926.]

